Wavelength Division Multiplexing (WDM), including without limitation Dense Wavelength Division Multiplexing (DWDM), are techniques that enable a multitude of optical wavelengths of differing frequencies to be transported over a single optical fiber. A DWDM network, for example, is constructed by interconnecting multiple DWDM network elements using glass optical fiber.
One limitation of maximum transmission distance over an optical fiber is chromatic dispersion, or spreading of optical pulses as they travel along the fiber. For single-mode optical fiber, chromatic dispersion occurs because the index of the glass varies slightly depending on the wavelength of the light, and the light associated with optical transmitters have nonzero spectral width. In order to combat the effects of chromatic dispersion, chromatic dispersion compensation devices and methods have been developed.
In known DWDM systems, chromatic dispersion compensation is often performed on each input fiber of each network element. Chromatic dispersion compensation can be carried out by using dispersion compensation fibers (DCF) or optical tunable dispersion compensators (OTDC). There continues to be a need for more cost effective solutions to the problem of chromatic dispersion in optical transmission systems. Preferably such compensation could be achieved by incorporating standardized compensation modules into optical network elements irrespective of length of the associated optical fiber. Further, it would be desirable if compensation processing could be carried out in real-time without any interruption of the flow of traffic in the respective optical fiber.